User-driven development in circuit breaker testing

Author: Niclas Wetterstrand and Nils Wäcklén

Circuit breaker analysers are key items in the toolkits of the hard-pressed test engineers in the power sector. There is no shortage of analysers on the market, but do they really meet users’ needs? Megger asked them. Niclas Wetterstrand, Megger’s Industry Director Utilities – Protection, and Nils Wäcklén, product owner of circuit breaker products at Megger, report on their answers and explain how these guided the development of an innovative instrument that sets new standards for speed, convenience, and safety in circuit breaker testing.

Our customers told us that the vast majority of circuit breaker tests they perform these days are standard measurements of contact resistance and main contact timing. There are two main reasons for this. First, circuit breaker reliability has improved over the years, which means that asset owners are now asking for less information to validate correct operation. Second, time and cost pressures have driven the adoption of a streamlined set of measurements, which are sufficient to confirm that the asset is working as intended, but no more.

In the past, there was time to acquire additional information by making a wider range of measurements, but now tests are often carried out by a subcontractor who gets paid a fixed amount per circuit breaker. This leaves no opportunity to carry out measurements that have not been explicitly requested. What’s needed today is the fastest possible way to get the job done, and this includes everything from collecting the test equipment from the stores, through to the test itself, and right up to returning the equipment to the stores.

With this in mind, Megger has developed a new circuit breaker analyser – the EGIL200 – to provide standard measurements that include main contact timing, PIR contact timing, auxiliary contact timing, station voltage and coil current. All these measurements can be made without the need to disconnect and reconnect the instrument. Additional facilities, which can be activated if and when needed, include motor current and motion measurements.

Main contact resistance (and PIR resistance value measurement) is also included in the standard measurements and is acquired with an external unit. Some instruments from other suppliers integrate contact resistance measurement within the main instrument and this might initially seem an attractive feature. Indeed, during discussions with customers, many asked for this, but after the pros and cons had been discussed, almost all changed their minds to favour a separate lightweight unit.

The only advantage of a built-in resistance measurement is that when they bring the instrument to the test location, users know they have everything they need to conduct the full range of standard measurements. However, this can easily be arranged when a separate resistance measurement unit is used simply by providing a transport case that will accommodate both this unit and the main instrument. On the other hand, the integrated solution has many disadvantages. For example, it means extra weight in the main unit, it limits options for performing measurements on items other than circuit breakers, and it requires the use of longer cables that add even more weight.

Another topic which came up frequently in the discussions with users is why it often takes around an hour to figure out how to connect the test cables, when actually performing the measurements takes only a few minutes. We have addressed this issue by looking carefully at every aspect of the design of the instrument and its associated accessories, including the transport case, cable bags, cables, test preparation, connection guidance, result evaluation, report creation, etc. We have found, for example, that with well thought out cable bag and cable design, colour coding and connection support, big savings can be made in overall testing time.

In particular, the cabling arrangements for our new instrument are convenient and practical for field use. Since users have told us that cable wear is an issue, the cables are designed to be durable, with thicker insulation and liberal use of cable sleeves. The cable bag has also been optimised to make it easy to carry while keeping the cables properly organised. For further convenience, the bag is equally suitable for use as a backpack, or as a handbag.

Test preparation and setup are other areas that our users told us were important and we’ve made a lot of effort to streamline these processes. Many instruments have a setup procedure that focuses on the test channel rather than the test object. By focusing on the test object and what needs to be measured, we have been able to reduce setup to a few clicks, with big time savings. Furthermore, if a similar asset of the same design needs to be tested, the basic tests can be repeated without the need for further settings.

Another thing we discovered from our discussions with users was that, in this era of outsourced breaker testing, the test engineer often does not have a specific test plan relating to the asset under test. Most often, the engineer will arrive on site and set up the test on the fly. Once again, this calls for a fast and streamlined setup procedure. To provide this, we involved a range of customers in trials of user-interface mock-ups during an early stage of the development project for our new instrument. We found that the biggest challenge was to provide a streamlined setup for basic measurements with a minimum of settings, while not unduly limiting the user’s flexibility.

We have achieved this by arranging for our new instrument to start with a quick-test menu, where the user selects the type of breaker to be tested, what needs to be measured and what operation should be performed. Initially, a connection screen is displayed to show how the test connections should be made and to confirm that they are correct. After that, the measurements are performed using the results and analysis screen. Last but not least, the instrument generates a report to provide evidence that the test was performed in line with contractual requirements and that either the circuit breaker meets its specification, or there is an issue that needs action or further investigation.

The option to produce professional reports with recommendations for further action without having to spend hours working on them in the office or hotel room was something engineers particularly wanted as an aid to reducing their workload. In addition, accurate and professional reports have been shown to give the contractor higher credibility with network owners and, in most cases, if the report recommends further action, the contractor is asked to provide it, which generates extra income.

As we have explained, the development of Megger’s new EGIL200 has been driven by the input from users, which ensures that it accurately and efficiently meets the requirements of today’s engineers. This means that EGIL200 is not just another test instrument, it’s a long-term partner which will help and support those who commission and maintain circuit breakers during difficult times as well as good times.